[PATCH v2 1/3] vhost-user: do not send RESET_OWNER on device reset

[Stefan Hajnoczi]

The VHOST_USER_RESET_OWNER message is deprecated in the spec:

   This is no longer used. Used to be sent to request disabling all
   rings, but some back-ends interpreted it to also discard connection
   state (this interpretation would lead to bugs).  It is recommended
   that back-ends either ignore this message, or use it to disable all
   rings.

The only caller of vhost_user_reset_device() is vhost_user_scsi_reset().
It checks that F_RESET_DEVICE was negotiated before calling it:

  static void vhost_user_scsi_reset(VirtIODevice *vdev)
  {
      VHostSCSICommon *vsc = VHOST_SCSI_COMMON(vdev);
      struct vhost_dev *dev = &vsc->dev;

      /*
       * Historically, reset was not implemented so only reset devices
       * that are expecting it.
       */
      if (!virtio_has_feature(dev->protocol_features,
                              VHOST_USER_PROTOCOL_F_RESET_DEVICE)) {
          return;
      }

      if (dev->vhost_ops->vhost_reset_device) {
          dev->vhost_ops->vhost_reset_device(dev);
      }
  }

Therefore VHOST_USER_RESET_OWNER is actually never sent by
vhost_user_reset_device(). Remove the dead code. This effectively moves
the vhost-user protocol specific code from vhost-user-scsi.c into
vhost-user.c where it belongs.

Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
---
 hw/scsi/vhost-user-scsi.c |  9 ---------
 hw/virtio/vhost-user.c    | 13 +++++++++----
 2 files changed, 9 insertions(+), 13 deletions(-)

diff --git a/hw/scsi/vhost-user-scsi.c b/hw/scsi/vhost-user-scsi.c
index ee99b19e7a..8582b2e8ab 100644
--- a/hw/scsi/vhost-user-scsi.c
+++ b/hw/scsi/vhost-user-scsi.c
@@ -71,15 +71,6 @@ static void vhost_user_scsi_reset(VirtIODevice *vdev)
     VHostSCSICommon *vsc = VHOST_SCSI_COMMON(vdev);
     struct vhost_dev *dev = &vsc->dev;
 
-    /*
-     * Historically, reset was not implemented so only reset devices
-     * that are expecting it.
-     */
-    if (!virtio_has_feature(dev->protocol_features,
-                            VHOST_USER_PROTOCOL_F_RESET_DEVICE)) {
-        return;
-    }
-
     if (dev->vhost_ops->vhost_reset_device) {
         dev->vhost_ops->vhost_reset_device(dev);
     }
diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index 8dcf049d42..7bed9ad7d5 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -1492,12 +1492,17 @@ static int vhost_user_reset_device(struct vhost_dev 
*dev)
 {
     VhostUserMsg msg = {
         .hdr.flags = VHOST_USER_VERSION,
+        .hdr.request = VHOST_USER_RESET_DEVICE,
     };
 
-    msg.hdr.request = virtio_has_feature(dev->protocol_features,
-                                         VHOST_USER_PROTOCOL_F_RESET_DEVICE)
-        ? VHOST_USER_RESET_DEVICE
-        : VHOST_USER_RESET_OWNER;
+    /*
+     * Historically, reset was not implemented so only reset devices
+     * that are expecting it.
+     */
+    if (!virtio_has_feature(dev->protocol_features,
+                            VHOST_USER_PROTOCOL_F_RESET_DEVICE)) {
+        return -ENOSYS;
+    }
 
     return vhost_user_write(dev, &msg, NULL, 0);
 }
-- 
2.41.0